The aim of this study was to develop a high-performance liquid chromatographic (HPLC) assay for the determination of moxifloxacin in human plasma and lung tissue. The assay was based on HPLC with a Supelcosil ABZ+ column and ultraviolet detection set at a wavelength of 296 nm. The extraction procedure was characterized by a fully automated liquid-solid extraction using an OASIS column for the solid phase. The assay has been found to be linear and validated over the concentration range 3.2 to 0.025 microg/ml for moxifloxacin in plasma and from 16 to 0.25 microg/g for moxifloxacin in lung tissue. In future, the assay will support the pharmacokinetic study of the penetration of moxifloxacin in human lung tissue.